Spool valve

ABSTRACT

A spool valve is equipped with a valve body, a spool arranged in a valve chamber such that the spool can be displaced between a first position, which allows communication between an inlet port and an outlet port, and a second position, which blocks communication between the inlet port and the outlet port, a pilot valve mechanism disposed in the valve body and which causes displacement of the spool along an axial direction under the pressure of a pilot fluid that acts on one end surface of the spool, and a spring that biases the spool toward one side in the axial direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2013-080458 filed on Apr. 8, 2013, thecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spool valve in which a spool isdisposed in a valve chamber of a valve body having an inlet port and anoutlet port formed therein.

2. Description of the Related Art

Heretofore, for example, in an air-jet loom in which wefts are made tofly out by jets of compressed air, a two-way valve has widely been used.With this type of air-jet loom, it is desirable for a high speed valvewith a large flow rate to be used. However, in the case that a two-wayvalve is used, because a large force is required instantaneously, adisadvantage results in that the solenoid coil that makes up the two-wayvalve is large in size with a commensurate increase in powerconsumption. Further, with such a two-way valve, the discharge flow rateand pressure cannot be controlled.

A spool valve is known in which the discharge flow rate and pressure canbe controlled. In such a spool valve, a spool is arranged in a valvechamber of a valve body having a plurality of ports formed therein, anda structure is provided in which the respective ports are opened andclosed by displacement of the spool in an axial direction. In relationto this type of spool valve, a technical concept is known in which, bycontrolling a current supplied to a proportional solenoid disposed inthe valve body, the spool is displaced directly and the pressure on thesecondary side of the spool is steadily controlled (see, e.g., JapaneseLaid-Open Patent Publication No. 08-285123).

SUMMARY OF THE INVENTION

A spool valve such as the one disclosed in Japanese Laid-Open PatentPublication No. 08-285123 is applied in a solenoid type in which anelectromagnetic force is used for moving the spool. For this reason, inthe case that a pressure fluid having a large flow rate is led out fromthe spool valve, a disadvantage results in that the solenoid coil mustbe made large in size together with a commensurate increase in powerconsumption.

The present invention has been made in consideration of theaforementioned problems, and has the object of providing a spool valve,which is capable of controlling a discharge flow rate and pressure, andof minimizing the size of the spool valve and reducing powerconsumption, even in the event that a pressure fluid having a large flowrate is led out from the spool valve.

To achieve the foregoing object, a spool valve according to the presentinvention comprises a valve body formed with a valve chamber, and aninlet port and an outlet port that open on a wall surface of the valvechamber and through which a pressure fluid flows, a spool arranged inthe valve chamber such that the spool can be displaced between a firstposition, which allows communication between the inlet port and theoutlet port, and a second position, which blocks communication betweenthe inlet port and the outlet port, a pilot valve mechanism disposed inthe valve body and which causes displacement of the spool along an axialdirection under the pressure of a pilot fluid that acts on one endsurface of the spool, and a spring that biases the spool toward one sidein the axial direction.

According to the spool valve of the present invention, because the spoolis displaced in an axial direction using a pressure of the pilot fluid,the lead out flow rate and pressure can be controlled, and even in theevent that a pressure fluid having a large flow rate is led out from thespool valve, the spool valve can be made smaller in size and powerconsumption can be reduced in comparison with a conventional solenoidtype of spool valve. Further, since the pressure of the pilot fluid canbe made to act directly on the one end surface of the spool, high speedresponsiveness and compactness of the spool valve can be achieved,without requiring a piston or the like that receives a pressure of thepilot fluid to be connected to the spool.

In the above-described spool valve, the pilot valve mechanism mayinclude a pilot fluid introduction passage that guides the pilot fluidto the one end surface of the spool, a pilot fluid discharge passagethrough which the pilot fluid is discharged, and a proportional valvedisposed in the pilot fluid introduction passage, and the spool isdisplaced corresponding to a degree of opening of the proportionalvalve.

In accordance with the above structure, since the spool can be displacedresponsive to the degree of opening of the proportional valve, with asimplified structure, the pressure (flow rate) of the pressure fluidthat is led out from the outlet port can be subjected to a proportionalcontrol.

The above-described spool valve may further comprise a first pressureacquiring means for acquiring a pressure of the pilot fluid that acts onthe one end surface of the spool, a second pressure acquiring means foracquiring a pressure of the pressure fluid led out from the outlet port,and a proportional valve control unit that controls the degree ofopening of the proportional valve based on the pressure acquired by thefirst pressure acquiring means and the pressure acquired by the secondpressure acquiring means.

In accordance with the above-described structure, the pressure (flowrate) of the pressure fluid that is led out from the outlet port can becontrolled to a desired pressure (flow rate).

The above-described pilot valve mechanism may include a pilot fluidintroduction passage that guides the pilot fluid to the one end surfaceof the spool, a pilot fluid discharge passage through which the pilotfluid is discharged, an introduction valve that switches the pilot fluidintroduction passage between an open condition and a closed condition, adischarge valve that switches the pilot fluid discharge passage betweenan open condition and a closed condition, an introduction valve controlunit that controls the introduction valve, and a discharge valve controlunit that controls the discharge valve.

In accordance with the above-described structure, by controlling openingand closing of the introduction valve and the discharge valve, with asimple structure, the pressure of the pilot fluid can be made to act onthe one end surface of the spool.

The above-described spool valve may further comprise an opening timesetting unit that sets a time of opening of the introduction valve,wherein the introduction valve control unit opens and closes theintroduction valve based on the time of opening set by the opening timesetting unit.

In accordance with the above-described structure, since the spool can bedisplaced corresponding to the time of opening for the introductionvalve that is set in the opening time setting unit, with a simplestructure, the pressure (flow rate) of the pressure fluid that is ledout from the outlet port can freely be controlled.

The above-described spool valve may further comprise a waiting timesetting unit that sets a waiting time from switching of the introductionvalve from the open condition to the closed condition until thedischarge valve is opened, wherein the discharge valve control unitmaintains the discharge valve in the closed condition until elapse ofthe waiting time set by the waiting time setting unit from switching ofthe introduction valve from the open condition to the closed condition.

In accordance with the above-described structure, since the waiting timeperiod until opening of the discharge valve from closure of theintroduction valve can be set in the waiting time setting unit, with asimple structure, the time during which the pressure fluid is led outfrom the outlet port can freely be controlled.

In the above-described spool valve, the introduction valve control unitmay open and close the introduction valve multiple times in succession.In this case, with a simple structure, the pressure (flow rate) of thepressure fluid led out from the outlet port can be raised in a stepwisefashion.

In the above-described spool valve, the discharge valve control unit mayopen and close the discharge valve multiple times in succession. In thiscase, with a simple structure, the pressure (flow rate) of the pressurefluid led out from the outlet port can be lowered in a stepwise fashion.

In the above-described spool valve, the discharge valve control unit mayopen the discharge valve with the introduction valve being in the opencondition. In accordance with this structure, compared to the case ofopening the discharge valve with the introduction valve being in aclosed condition, the pressure (flow rate) of the pressure fluid led outfrom the outlet port can be decreased gradually.

In the above-described spool valve, the pilot valve mechanism mayfurther include a proportional valve disposed in the pilot fluidintroduction passage, the introduction valve control unit may open andclose the introduction valve under a condition in which the proportionalvalve is open, and the discharge valve control unit may open and closethe discharge valve under a condition in which the proportional valve isopen.

In accordance with the above-described structure, the pressure (flowrate) of the pressure fluid that is led out from the outlet port can becontrolled efficiently to a desired pressure (flow rate).

In the above-described spool valve, a discharge port that opens on awall surface of the valve chamber may be formed in the valve body, andin a condition in which the spool is positioned at the second position,communication is established between the outlet port and the dischargeport, and in a condition in which the spool is positioned at the firstposition, communication is blocked between the outlet port and thedischarge port.

In accordance with such a structure, since the outlet port and thedischarge port are placed in communication in a state in whichcommunication between the inlet port and the outlet port is blocked, thepressure fluid from the outlet port can be discharged to the exteriorfrom the discharge port. Consequently, compared to a situation in whichthe discharge port is not provided, the pressure (flow rate) of thepressure fluid can be decreased rapidly.

According to the present invention, because the spool is displaced in anaxial direction using a pressure of the pilot fluid, the lead out flowrate and pressure can be controlled, and even in the event that apressure fluid having a large flow rate is led out from the spool valve,the spool valve can be made smaller in size and power consumption can bereduced in comparison with a conventional solenoid type of spool valve.Further, since the pressure of the pilot fluid can be made to actdirectly on the one end surface of the spool, high speed responsivenessand compactness of the spool valve can be achieved, without requiring apiston or the like that receives a pressure of the pilot fluid to beconnected to the spool.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which a preferredembodiment of the present invention is shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a spool valve according to an embodimentof the present invention;

FIG. 2 is an exploded perspective view of the spool valve;

FIG. 3 is a cross sectional view taken along line III-III of FIG. 1;

FIG. 4 is a cross sectional view taken along line IV-IV of FIG. 1;

FIG. 5 is a cross sectional view taken along line V-V of FIG. 1;

FIG. 6 is a view of a circuit diagram for the spool valve;

FIG. 7 is an explanatory drawing showing a state in which the spool thatconstitutes the spool valve shown in FIG. 3 is displaced to a firstposition;

FIG. 8 is an explanatory diagram of a control method for the spoolvalve;

FIG. 9 is an explanatory diagram of a control method for a spool valveaccording to a first modification;

FIG. 10 is an explanatory diagram of a control method for a spool valveaccording to a second modification;

FIG. 11 is an explanatory diagram of a control method for a spool valveaccording to a third modification;

FIG. 12 is an explanatory diagram of a control method for a spool valveaccording to a fourth modification; and

FIG. 13 is an explanatory diagram of a control method for a spool valveaccording to a fifth modification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, a preferred embodiment of a spool valve according to the presentinvention and a control method in relation thereto will be describedwith reference to the accompanying drawings.

As shown in FIGS. 1 and 2, a spool valve 10 according to the presentembodiment is equipped with a spool valve main body 12, a pilot valvemechanism 14 disposed in the spool valve main body 12, a cover member 18that surrounds the pilot valve mechanism 14, and a controller 20.

As shown in FIG. 3, the spool valve main body 12 includes a block-shapedvalve body 22, a cylindrical sleeve 26 arranged in a valve chamber 24that opens on one end surface of the valve body 22, a spool (main valve)28 arranged in the interior of the sleeve 26 such that the spool 28 canbe displaced (slidably moved) along the axial direction of the sleeve26, a spring 30 that biases the spool 28 toward one end side, a pair ofannular end plates 32, 34 provided on both sides in the axial directionof the sleeve 26, and a retaining plate 36 disposed on the one endsurface of the valve body 22.

The valve body 22 has a breathing port 38 which opens on an abutmentsurface 37 of the wall surfaces making up the valve chamber 24, theabutment surface 37 being directed toward one end of the spool 28,wherein the end plate 32 abuts against the abutment surface 37. Thebreathing port 38 takes in and exhausts air on the other end side of thespool 28. Further, in the valve body 22, an inlet port 40, an outletport 42, and a discharge port (exhaust port) 44, which open on a wallsurface making up the valve chamber 24, are formed successively in thisorder at equal intervals along the axial direction of the spool 28. Morespecifically, the outlet port 42 is positioned between the inlet port 40and the discharge port 44.

As can be understood from FIG. 6, the inlet port 40 communicates with apressure fluid introduction passage 48 connected to a pressure fluidsupply source 46, and the outlet port 42 communicates with a pressurefluid lead out passage 52 connected to a nozzle 50. More specifically,the spool valve 10 according to the present embodiment can be used in anair-jet loom in which the pressure fluid is ejected out from the nozzle50 so as to enable wefts to be ejected.

A first hole 54 that communicates with the inlet port 40, a second hole56 that communicates with the outlet port 42, and a third hole 58 thatcommunicates with the discharge port 44 are formed respectively in thesleeve 26. Movement of the sleeve 26 in the axial direction isrestricted as a result of the sleeve 26 being sandwiched between thepair of end plates 32, 34. A plurality of ring grooves 64 (four in theillustrated example) are formed on the outer circumferential surface ofthe sleeve 26 with sealing members 60 being disposed therein. The ringgrooves 64 are positioned on both sides of the first through third holes54, 56, 58, respectively.

The spool 28 is formed with a length that is shorter than the totallength of the sleeve 26, and has a shape in which an annular recess 66is formed roughly in the center along the axial direction of acylindrical member. More specifically, the spool 28 is of a shape suchthat two large diameter portions 68, 70 are connected through a narrowmiddle portion 72. The outer circumferential surfaces of the respectivelarge diameter portions 68, 70 are arranged in sliding contact with theinner surface of the sleeve 26.

With the present embodiment, in a condition in which the other endsurface of the spool 28 is positioned at the other end of the sleeve 26(i.e., when the spool 28 is located at a first position), the inlet port40 and the outlet port 42 communicate with each other through theannular recess 66, whereas communication between the outlet port 42 andthe discharge port 44 is blocked. Further, in a condition in which theone end surface of the spool 28 is positioned at the one end of thesleeve 26 (i.e., when the spool 28 is located at a second position),communication between the inlet port 40 and the outlet port 42 isblocked, whereas the outlet port 42 and the discharge port 44communicate with each other through the annular recess 66 (see FIG. 7).

A helical compression spring or coil spring, for example, can be used asthe spring 30. One end of the spring 30 is arranged in a recess 71formed in the other end surface of the spool 28, and the other end ofthe spring 30 is arranged in a recess 73 formed in the abutment surface37 of the valve chamber 24. Consequently, the spool 28 is biased orurged toward the one end side by the spring 30.

In a condition with the end plate 34 mounted thereon, the retainingplate 36 is fixed to the valve body 22 by a bolt 74 (see FIGS. 2 and 5).A communication passage 78, which communicates with the interior of thesleeve 26 (valve chamber 24) through a central hole 76 in the end plate34, is formed in the retaining plate 36.

A first pressure sensor (first pressure acquiring means) 80 foracquiring the pressure of a pilot fluid that acts on the one end surfaceof the spool 28 is disposed in the retaining plate 36. The firstpressure sensor 80 is capable of contacting the pilot fluid, which isguided from the interior of the sleeve 26 (valve chamber 24) through apenetrating hole 82 formed in the end plate 34. Further, in the presentembodiment, a second pressure sensor (second pressure acquiring means)84 for acquiring a pressure on the secondary side of the spool 28 isdisposed in the pressure fluid lead out passage 52 (see FIG. 6).

As shown in FIGS. 2 through 6, the pilot valve mechanism 14 is amechanism that causes the pressure of the pilot fluid to act on the oneend surface of the spool 28. The pilot valve mechanism 14 includes anadapter plate 86, a proportional valve, 88, an introduction valve 90,and a discharge valve 92.

The adapter plate 86 is fixed to one end surface of the retaining plate36. A pilot fluid introduction passage 94 for introducing the pilotfluid to one end surface of the spool 28, and a pilot fluid dischargepassage 96 for discharging the pilot fluid are formed in the adapterplate 86 (see FIG. 6). The pilot fluid introduction passage 94 isconnected to the pressure fluid introduction passage 48. Detailsconcerning the structure of the pilot fluid introduction passage 94 andthe pilot fluid discharge passage 96 will be described later.

The proportional valve 88 serves to open and close the pilot fluidintroduction passage 94, and includes a proportional valve main body 98,a first port 100 to which the pilot fluid is introduced, and a secondport 102 through which the pilot fluid is led out (see FIG. 3).

As can be understood from FIG. 6, the introduction valve 90 is disposedin parallel with the proportional valve 88 and functions as a two-wayvalve that opens and closes the pilot fluid introduction passage 94. Theintroduction valve 90 includes an introduction valve main body 104, afirst port 106 to which the pilot fluid is introduced, and a second port108 through which the pilot fluid is led out (see FIG. 4).

The discharge valve 92 is constituted as a two-way valve that opens andcloses the pilot fluid discharge passage 96. The discharge valve 92includes a discharge valve main body 110, a first port 112 to which thepilot fluid is introduced, and a second port 114 through which the pilotfluid is led out (see FIG. 5).

The pilot fluid introduction passage 94 includes a first introductionpassage 116 that guides the pressure fluid from the pressure fluidintroduction passage 48 to the first port 100 of the proportional valve88, a second introduction passage 118 that guides the pressure fluid tothe first port 106 of the introduction valve 90, a third introductionpassage 120 that guides the pilot fluid, which has been led out from thesecond port 102 of the proportional valve 88, to the one end surface ofthe spool 28, and a fourth introduction passage 122 that guides thepilot fluid, which has been led out from the second port 108 of theintroduction valve 90, to the one end surface of the spool 28. The firstintroduction passage 116 and the second introduction passage 118communicate with each other, and the third introduction passage 120 andthe fourth introduction passage 122 communicate with each other.

The pilot fluid discharge passage 96 contains a first discharge passage124 that guides the pilot fluid, which has been directed to the one endsurface of the spool 28, to the first port 112 of the discharge valve92, and a second discharge passage that discharges, to the exterior, thepilot fluid that has been led out from the second port 114 of thedischarge valve 92. The first discharge passage 124 communicates withthe third introduction passage 120 and the fourth introduction passage122.

The controller 20 includes a plurality of wiring boards 127, 128, 129(three in the illustrated example), which are connected electrically tothe first pressure sensor 80, the proportional valve 88, theintroduction valve 90, and the discharge valve 92, and a connectionterminal 130 disposed on the wiring board 129 and connected to anon-illustrated external device.

As shown in FIG. 6, the controller 20, which is controlled by signalsfrom an external device, includes a proportional valve control unit 132,an introduction valve control unit 134, a discharge valve control unit136, an opening time setting unit 138, and a waiting time setting unit140. More specifically, transmission and reception of signals (analogsignals or digital signals) between the controller 20 and the externaldevice may be carried out by way of wireless communications or wiredcommunications. Further, the controller 20 receives signals (pressurewaveform signals) output from the external device, for example, andbased on such signals, controls opening and closing of the proportionalvalve 88, the introduction valve 90, and the discharge valve 92. At thistime, the controller 20 receives signals output from at least one of thefirst pressure sensor 80 and the second pressure sensor 84, and iscapable of effecting feedback controls on the proportional valve 88, theintroduction valve 90, and the discharge valve 92.

Although in the present embodiment, the proportional valve control unit132, the introduction valve control unit 134, the discharge valvecontrol unit 136, the opening time setting unit 138, and the waitingtime setting unit 140 are disposed on the plural wiring boards 127, 128,129, the control units may be provided on the aforementioned externaldevice. In the case that the proportional valve control unit 132, theintroduction valve control unit 134, the discharge valve control unit136, the opening time setting unit 138, and the waiting time settingunit 140 are disposed on the external device, since the wiring boards127, 128, 129 can be simplified in structure (for example, some of thewiring boards 127, 128, 129 can be eliminated), the spool valve 10 canbe further reduced in size.

The proportional valve control unit 132 controls the degree of openingof the proportional valve 88 based on output signals output from atleast one of the first pressure sensor 80 and the second pressure sensor84. The introduction valve control unit 134 controls opening and closingof the introduction valve 90, and the discharge valve control unit 136controls opening and closing of the discharge valve 92. The opening timesetting unit 138 sets a time of opening of the introduction valve 90,and the waiting time setting unit 140 sets a waiting time from switchingof the introduction valve 90 from the open condition to the closedcondition until the discharge valve 92 is opened.

The spool valve 10 according to the present embodiment is constructedbasically as described above. Next, a method of controlling the spoolvalve 10 will be described.

In an initial condition of the present embodiment, each of theproportional valve 88, the introduction valve 90, and the dischargevalve 92 is closed. More specifically, because the pilot fluid is notsupplied to the spool valve main body 12, the spool 28 is pressed by thespring 30 and is placed in the second position (see FIG. 7). Statedotherwise, since communication between the inlet port 40 and the outletport 42 is blocked, ejection of pressure fluid from the nozzle 50 isstopped.

With the control method according to the present embodiment, at first,the opening time setting unit 138 sets the opening time of theintroduction valve 90 to time t1, and the waiting time setting unit 140sets the waiting time to time t2. The times t1 and t2, for example, aredetermined based on a necessary pressure or flow rate, etc., requiredfor the pressure fluid to be ejected from the nozzle 50, and are storedbeforehand in the controller 20.

Next, as shown in FIG. 8, the introduction valve control unit 134 opensthe introduction valve 90 for the time t1 that was set by the openingtime setting unit 138. When the introduction valve 90 is opened, thepilot fluid, which is led out from the second port 108 of theintroduction valve 90, is guided to the one end surface of the spool 28through the fourth introduction passage 122, the communication passage78 of the retaining plate 36, and the hole 76 of the end plate 34. Morespecifically, the pressure of the pilot fluid acts on the one endsurface of the spool 28, whereupon the spool 28 is displaced to theother end side while compressing the spring 30. In the presentembodiment, the spool 28 is displaced from the second position to thefirst position. At this time, the pressure of the pilot fluid that actson the one end surface of the spool (hereinafter referred to as a “firstpressure”) reaches a pressure P1 a.

Further, since the inlet port 40 and the outlet port 42 are placed incommunication when the spool 28 is displaced to the first position, thepressure fluid from the inlet port 40 flows into the outlet port 42 viathe annular recess 66 of the spool 28. In addition, the pressure fluidthat was guided to the outlet port 42 passes through the pressure fluidlead out passage 52 and is ejected from the nozzle 50. At this time, thepressure of the pressure fluid that flows through the pressure fluidlead out passage 52 (hereinafter referred to as a “second pressure”)reaches a pressure P1 b.

Additionally, upon closure of the introduction valve 90, the firstpressure is maintained at the pressure P1 a, together with the secondpressure being maintained at the pressure P1 b. More specifically, thepressure fluid is ejected at a constant pressure from the nozzle 50.

Next, the discharge valve control unit 136 maintains the closed state ofthe discharge valve 92 until elapse of the time t2 after closing of theintroduction valve 90. During such a closed state, the pressure fluidcontinues to be ejected from the nozzle 50. At this time, the secondpressure is maintained at the pressure P1 b.

Further, after time t2 elapses from closing of the introduction valve90, the discharge valve control unit 136 opens and closes the dischargevalve 92. When the discharge valve 92 is opened, the pilot fluid isdischarged to the exterior through the first discharge passage 124, thefirst port 112 of the discharge valve 92, the second port 114 of thedischarge valve 92, and the second discharge passage 126. When this isdone, since the first pressure is lowered, the spool 28 is pressed bythe spring 30 and is restored to the second position.

When the spool is restored to the second position, communication betweenthe inlet port 40 and the outlet port 42 is interrupted, whereas theoutlet port 42 and the discharge port 44 are placed in communication.Consequently, the pressure fluid from the pressure fluid lead outpassage 52 is discharged to the exterior through the outlet port 42, theannular recess 66 of the spool 28, and the discharge port 44. Thus,ejection of the pressure fluid from the nozzle 50 is stopped.

As described above, according to the present embodiment, because thespool 28 is displaced in an axial direction using a pressure of thepilot fluid, the flow rate (lead out flow rate) and pressure of thepressure fluid flowing out from the outlet port 42 can be controlled,while in addition, the spool valve 10 can be made smaller in size andpower consumption can be reduced in comparison with a conventionalsolenoid type of spool valve. Further, since the pressure of the pilotfluid can be made to act directly on the one end surface of the spool28, high speed responsiveness and compactness of the spool valve 10 canbe achieved, without requiring a piston or the like that receives apressure of the pilot fluid to be connected to the spool 28.

Further, since the outlet port 42 and the discharge port 44 are placedin communication in a state in which communication is blocked betweenthe inlet port 40 and the outlet port 42, the pressure fluid from theoutlet port 42 can be discharged to the exterior from the discharge port44. Consequently, compared to a situation in which the discharge port 44is not provided, the pressure (flow rate) of the pressure fluid can bedecreased rapidly.

Furthermore, according to the present embodiment, by controlling openingand closing of the introduction valve 90 and the discharge valve 92,with a simple structure, the pressure of the pilot fluid can be made toact on the one end surface of the spool 28.

In the present embodiment, in the event that control is performed in theforegoing manner, the proportional valve 88 and the proportional valvecontrol unit 132 may be dispensed with. In this case, the structure ofthe spool valve 10 can be further reduced in size. The same holds truefor the first modification and the third modification, which will bedescribed below.

(Modification 1)

Next, a control method for a spool valve 10 according to a firstmodification of the present embodiment will be described with referenceto FIG. 9.

With the present modification, as shown in FIG. 9, at first, the openingtime setting unit 138 sets the opening time of the introduction valve 90to time t3, and the waiting time setting unit 140 sets the waiting timeto time t4. In this case, the time t3 is half of the time t1, and thetime t4 is half of the time t2. The times t3 and t4, for example, areset based on the required pressure or flow rate, etc., needed for thepressure fluid to be ejected from the nozzle 50, and are storedbeforehand in the controller 20.

Next, the introduction valve control unit 134 opens the introductionvalve 90 for the time t3 that was set by the opening time setting unit138. Upon opening of the introduction valve 90, the spool 28 isdisplaced to the other end side while the spool 28 compresses the spring30. At this time, since the first pressure reaches the pressure P2 a(which is one half of the pressure P1 a), the spool 28 becomes placed ata position between the first position and the second position. When thisis done, compared to the case of the first pressure being the pressureP1 a, since the degree of opening of the communication passage betweenthe inlet port 40 and the outlet port 42 is smaller (i.e., becomes onehalf of the case of the pressure P1 a), the pressure (second pressure)of the pressure fluid in the pressure fluid lead out passage 52 reachesthe pressure P2 b (which is one half of the pressure P1 b). In addition,when the introduction valve 90 is closed, the first pressure ismaintained at the pressure P2 a, together with the second pressure beingmaintained at the pressure P2 b.

Next, the discharge valve control unit 136 maintains the closed state ofthe discharge valve 92 until elapse of the time t4 after closing of theintroduction valve 90. Upon doing so, during such a closed state, thepressure fluid continues to be ejected from the nozzle 50. At this time,the second pressure is maintained at the pressure P2 b.

Further, the discharge valve control unit 136 opens and closes thedischarge valve 92 after the time t4 elapses from closing of theintroduction valve 90. When the discharge valve 92 is opened, since thespool 28 is restored to the second position, ejection of the pressurefluid from the nozzle 50 is stopped.

As can be understood from the present modification, with the presentembodiment, by controlling the opening time (times t1, t3) of theintroduction valve 90, the pressure (flow rate) of the pressure fluidthat is led out from the outlet port 42 can be controlled. Further, bycontrolling the waiting time (times t2, t4) from switching of theintroduction valve 90 from the open state to the closed state until thedischarge valve 92 is opened, the timing at which the pressure fluid isejected from the outlet port 42 can also be controlled.

More specifically, according to the present embodiment, because thespool 28 can be displaced corresponding to the opening time of theintroduction valve 90, which is set by the opening time setting unit138, with a simple structure, the pressure (flow rate) of the pressurefluid that is led out from the outlet port 42 can freely be controlled.

Further, according to the present embodiment, since the waiting timeperiod until opening of the discharge valve 92 after closing of theintroduction valve 90 can be set in the waiting time setting unit 140,with a simple structure, the timing at which the pressure fluid is ledout from the outlet port 42 can freely be controlled.

(Modification 2)

Next, a control method for a spool valve 10 according to a secondmodification of the present embodiment will be described with referenceto FIG. 10.

With the present modification, as shown in FIG. 10, the discharge valvecontrol unit 136 opens the discharge valve 92, together with theproportional valve control unit 132 opening the proportional valve 88.When the proportional valve 88 is opened, the pilot fluid, which is ledout from the second port 102 of the proportional valve 88, is guided tothe one end surface of the spool 28 via the third introduction passage120, the communication passage 78 of the retaining plate 36, and thehole 76 of the end plate 34. More specifically, the pressure of thepilot fluid acts on the one end surface of the spool 28. When acted onby the pilot fluid, the spool 28 is displaced to the other end sidewhile compressing the spring 30. Upon displacement of the spool 28 tothe other end side, since the inlet port 40 and the outlet port 42 areplaced in communication, the pressure fluid that is led out from theoutlet port 42 is ejected from the nozzle 50.

At this time, the discharge valve 92 is opened. Due to the fact that theinflow rate from the proportional valve 88 exceeds the discharge ratefrom the discharge valve 92, the pressure of the pilot fluid that actson the one end surface of the spool 28 and the pressure of the pressurefluid that is led out from the outlet port 42 can be controlled.Further, the proportional valve control unit 132 controls the degree ofopening of the proportional valve 88 based on the pressure acquired bythe first pressure sensor 80 and the pressure acquired by the secondpressure sensor 84. With the present modification, the proportionalvalve control unit 132 gradually increases the degree of opening of theproportional valve 88. Upon doing so, the first pressure and the secondpressure gradually rise. Furthermore, the proportional valve controlunit 132 gradually decreases the degree of opening of the proportionalvalve 88. Upon doing so, the first pressure and the second pressuregradually are lowered. With the present modification, after elapse of apredetermined time, the proportional valve control unit 132 closes theproportional valve 88, and the discharge valve control unit 136 closesthe discharge valve 92.

According to the present modification, since the spool 28 can bedisplaced responsive to the degree of opening of the proportional valve88, with a simple structure, the pressure (flow rate) of the pressurefluid led out from the outlet port 42 can be subjected to a proportionalcontrol.

Further, since the proportional valve control unit 132 controls thedegree of opening of the proportional valve 88 based on the pressureacquired by the first pressure sensor 80 and the pressure acquired bythe second pressure sensor 84, the pressure (flow rate) of the pressurefluid led out from the outlet port 42 can be controlled to a desiredpressure (flow rate).

The present modification is not limited to performing the controlprecisely as described above. For example, the proportional valvecontrol unit 132 may increase the degree of opening of the proportionalvalve 88 in a stepwise manner. In this case, the first pressure and thesecond pressure can be raised in a stepwise manner. Further, theproportional valve control unit 132 may decrease the degree of openingof the proportional valve 88 gradually (continuously) or in a stepwisemanner.

In the case of implementing the present modification, the introductionvalve 90 and the introduction valve control unit 134 may be dispensedwith. In this case, the structure of the spool valve 10 can be furtherreduced in size. Further, the discharge valve 92 and the discharge valvecontrol unit 136 may be dispensed with. In this case, the pilot fluid isalways discharged at a constant discharge rate from the pilot fluiddischarge passage 96. In addition, by causing the pilot fluid to be ledout from the second port 102 of the proportional valve 88 in an amountthat is greater than the aforementioned discharge rate, the pressure ofthe pilot fluid can be made to act on the one end surface of the spool28. Consequently, the structure of the spool valve 10 can be made evensmaller in size.

(Modification 3)

Next, a spool valve 10 according to a third modification of the presentembodiment will be described with reference to FIG. 11. With the presentmodification, as shown in FIG. 11, after the introduction valve controlunit 134 has opened and closed the introduction valve a plurality oftimes (two times in the illustrated example) in succession, thedischarge valve control unit 136 then opens the discharge valve 92 aplurality of times (two times in the illustrated example) in succession.When this is done, the first pressure and the second pressure are raisedstepwise, and thereafter, the first pressure and the second pressure arelowered stepwise. In this manner, according to the present modification,with a simple structure, the pressure (flow rate) of the pressure fluidthat is led out from the outlet port 42 can be raised in a stepwisemanner as well as lowered in a stepwise manner.

(Modification 4)

Next, a spool valve 10 according to a fourth modification of the presentembodiment will be described with reference to FIG. 12. With the presentmodification, as shown in FIG. 12, in a condition in which theintroduction valve control unit 134 maintains the introduction valve 90in an open state, the discharge valve control unit 136 also opens thedischarge valve 92. Upon doing so, after the first pressure and thesecond pressure are raised and have reached a constant pressure, thefirst pressure and the second pressure are decreased in a comparativelymoderate fashion. In this manner, according to the present modification,compared to the case of opening the discharge valve 92 in a state inwhich the introduction valve 90 has been closed, the pressure (flowrate) of the pressure fluid that is led out from the outlet port 42 canbe decreased more gradually.

(Modification 5)

Next, a spool valve 10 according to a fifth modification of the presentembodiment will be described with reference to FIG. 13. With the presentmodification, as shown in FIG. 13, in a condition in which theproportional valve control unit 132 maintains the proportional valve 88in an open state, the introduction valve control unit 134 opens andcloses the introduction valve 90, and the discharge valve control unit136 opens and closes the discharge valve 92. When this is done, thefirst pressure and the second pressure are first raised gradually andthereafter raised at a greater rate. Further, after being decreased at agreater rate, the first pressure and the second pressure then aredecreased more gradually.

According to the present modification, since the introduction valve 90and the discharge valve 92 are opened and closed in a state in which theproportional valve is kept open, with a simple structure, the pressure(flow rate) of the pressure fluid that is led out from the outlet port42 can be controlled efficiently to a desired pressure (flow rate).

The present modification is not limited to performing the control in theabove-described manner. For example, while the proportional valve 88 isin an open condition, the introduction valve control unit 134 may openand close the introduction valve 90 a plurality of times, and thedischarge valve control unit 136 may open and close the discharge valve92 a plurality of times.

Although a preferred embodiment of the present invention has beenpresented above, the spool valve according to the present invention isnot limited to this embodiment, and various changes and modificationsmay be made thereto without departing from the scope of the invention asset forth in the appended claims.

What is claimed is:
 1. A spool valve comprising: a valve body formedwith a valve chamber, and an inlet port and an outlet port that open ona wall surface of the valve chamber and through which a pressure fluidflows; a spool arranged in the valve chamber such that the spool isdisplaceable between a first position, which allows communicationbetween the inlet port and the outlet port, and a second position, whichblocks communication between the inlet port and the outlet port; a pilotvalve mechanism disposed in the valve body and which causes displacementof the spool along an axial direction under a pressure of a pilot fluidthat acts on only one end surface of the spool; and a spring that biasesthe spool toward one side in the axial direction.
 2. The spool valveaccording to claim 1, wherein the pilot valve mechanism includes: apilot fluid introduction passage that guides the pilot fluid to the oneend surface of the spool; a pilot fluid discharge passage through whichthe pilot fluid is discharged; and a proportional valve disposed in thepilot fluid introduction passage, and the spool is displacedcorresponding to a degree of opening of the proportional valve.
 3. Thespool valve according to claim 2, further comprising: first pressureacquiring means for acquiring a pressure of the pilot fluid that acts onthe one end surface of the spool; second pressure acquiring means foracquiring a pressure of the pressure fluid led out from the outlet port;and a proportional valve control unit that controls the degree ofopening of the proportional valve based on the pressure acquired by thefirst pressure acquiring means and the pressure acquired by the secondpressure acquiring means.
 4. The spool valve according to claim 1,wherein the pilot valve mechanism includes: a pilot fluid introductionpassage that guides the pilot fluid to the one end surface of the spool;a pilot fluid discharge passage through which the pilot fluid isdischarged; an introduction valve that switches the pilot fluidintroduction passage between an open condition and a closed condition; adischarge valve that switches the pilot fluid discharge passage betweenan open condition and a closed condition; an introduction valve controlunit that controls the introduction valve; and a discharge valve controlunit that controls the discharge valve.
 5. The spool valve according toclaim 4, further comprising: an opening time setting unit that sets atime of opening of the introduction valve, wherein the introductionvalve control unit opens and closes the introduction valve based on thetime of opening set by the opening time setting unit.
 6. The spool valveaccording to claim 4, further comprising: a waiting time setting unitthat sets a waiting time from switching of the introduction valve fromthe open condition to the closed condition until the discharge valve isopened, wherein the discharge valve control unit maintains the dischargevalve in the closed condition until elapse of the waiting time set bythe waiting time setting unit from switching of the introduction valvefrom the open condition to the closed condition.
 7. The spool valveaccording to claim 4, wherein the introduction valve control unit opensand closes the introduction valve multiple times in succession.
 8. Thespool valve according to claim 4, wherein the discharge valve controlunit opens and closes the discharge valve multiple times in succession.9. The spool valve according to claim 4, wherein the discharge valvecontrol unit opens the discharge valve with the introduction valve beingin the open condition.
 10. The spool valve according to claim 4,wherein: the pilot valve mechanism further includes a proportional valvedisposed in the pilot fluid introduction passage; the introduction valvecontrol unit opens and closes the introduction valve under a conditionin which the proportional valve is open; and the discharge valve controlunit opens and closes the discharge valve under a condition in which theproportional valve is open.
 11. The spool valve according to claim 1,wherein: a discharge port that opens on the wall surface of the valvechamber is formed in the valve body; and in a condition in which thespool is positioned at the second position, communication is establishedbetween the outlet port and the discharge port, and in a condition inwhich the spool is positioned at the first position, communication isblocked between the outlet port and the discharge port.
 12. The spoolvalve according to claim 2, further comprising: a first pressure sensorto acquire a pressure of the pilot fluid that acts on the one endsurface of the spool; a second pressure sensor to acquire a pressure ofthe pressure fluid led out from the outlet port; and a proportionalvalve control unit that controls the degree of opening of theproportional valve based on the pressure acquired by the first pressuresensor and the pressure acquired by the second pressure sensor.
 13. Aspool valve comprising: a valve body formed with a valve chamber, and aninlet port and an outlet port that open on a wall surface of the valvechamber and through which a pressure fluid flows; a spool arranged inthe valve chamber such that the spool is displaceable between a firstposition, which allows communication between the inlet port and theoutlet port, and a second position, which blocks communication betweenthe inlet port and the outlet port; a pilot valve mechanism disposed inthe valve body and which causes displacement of the spool along an axialdirection under a pressure of a pilot fluid that acts on one end surfaceof the spool; and a spring that biases the spool toward one side in theaxial direction, wherein the pilot valve mechanism includes: a pilotfluid introduction passage that guides the pilot fluid to the one endsurface of the spool, a pilot fluid discharge passage through which thepilot fluid is discharged, and a proportional valve disposed in thepilot fluid introduction passage, and the spool is displacedcorresponding to a degree of opening of the proportional valve.
 14. Aspool valve comprising: a valve body formed with a valve chamber, and aninlet port and an outlet port that open on a wall surface of the valvechamber and through which a pressure fluid flows; a spool arranged inthe valve chamber such that the spool is displaceable between a firstposition, which allows communication between the inlet port and theoutlet port, and a second position, which blocks communication betweenthe inlet port and the outlet port; a pilot valve mechanism disposed inthe valve body and which causes displacement of the spool along an axialdirection under a pressure of a pilot fluid that acts on one end surfaceof the spool; and a spring that biases the spool toward one side in theaxial direction, wherein the pilot valve mechanism includes: a pilotfluid introduction passage that guides the pilot fluid to the one endsurface of the spool, a pilot fluid discharge passage through which thepilot fluid is discharged, an introduction valve that switches the pilotfluid introduction passage between an open condition and a closedcondition, a discharge valve that switches the pilot fluid dischargepassage between an open condition and a closed condition, anintroduction valve control unit that controls the introduction valve,and a discharge valve control unit that controls the discharge valve.